California Proposition 65
Proposition 65 requires that a warning must be posted on any product that contains or may contain any of more than 800 elements that the California Air Resources Board considers harmful. The warning does not mean that these products will necessarily cause cancer or reproductive harm. Moreover, a Prop 65 warning does not mean a product is in violation of any product-safety standards or requirements. In fact, the California government has clarified that “the fact that a product bears a Proposition 65 warning does not mean by itself that the product is unsafe.” The government has also explained that “You could think of Proposition 65 more as a ‘right to know’ law than a pure product safety law.”
Example: "WARNING: This product contains a chemical known to the state of California to cause cancer, birth defects, and/or reproductive harm."
Chemical List: https://oehha.ca.gov/proposition-65/proposition-65-list